How to create realistic cuts in ZBrush

A free ZBrush 4 tutorial to get you cutting, stitching and PolyPainting monsters in no time, with results that will make Frankenstein himself green with envy!

Expert Ted Lockwood teaches us how to use ZBrush 4 to create an open wound with stitches over flesh…

Time needed: Approx 30-45 minutes

One of the most classic – and practical – monster features is the grotesque stitching that holds huge wounds shut and totally unrelated body parts together.

From Frankenstein’s monster to the Reavers in Firefly and Serenity, they tell everyone that this creature is way too scary to wait for his wounds to heal. Whether it’s done with thread, rope or giant metal staples, a monster is only as frightening as the horrific wounds it’s ignoring while it hunts you down!

In this article, I’ll show how to sculpt and PolyPaint a nasty rough gash held together with whatever the mad scientist could find lying around his lab, using a simple process that can be applied to a host of similarly classic monster features.

Real stitches are generally simple, clean and – let’s be honest – boring. While exploring ways to sculpt monster-style cuts and stitches, I found that one of the most important elements was to let mistakes happen. Monsters aren’t generally very clean and tidy, and neither are their doctors.

Using loose, quick strokes for the base shape of the cut will add a sloppy, naturally random element. Keeping this in mind throughout the entire process will help take the gross, chunky look of the stitching to the next level of nastiness.

This guide will add another tool to your mental library of features for use with your future characters. Try applying this technique to things like chains piercing a demon’s skin to hold his armour in place, or the intersections between a cyborg’s organic and technological parts.

You can also choose to follow this tutorial sculpting on a plane like I have, then using ZBrush’s GrabDoc feature in the Alpha menu to turn your cut and stitches into an alpha that can be reused on other characters.

Every character has its own style and story that affects the design of the stitching. So before you start operating on your character, think about how it would have received its wound, and how it was stitched up. Did they get into a huge chainsaw fight with a robot, creating a jagged, torn gash? Or perhaps were they assembled from pieces of other monsters by an evil surgeon, who used clean cuts and a tight stitch? Is the creature so enraged that some of the giant metal staples have started to pull apart? Should there be some gore poking out between the stitches?

Once these basic design elements are established, we’re ready to begin.

Step 1 – Make the cut

First, choose the shape and location of your cut. Use the Standard brush and hold Opt/Alt to cut a jagged, wandering line across your model. Now use the Pinch brush to close the gash a bit, and the Inflate brush along the edges to give it a puffy, inflamed look. Using the Standard brush with Lazy Mouse turned off, make a series of holes along the cut for the stitches.

Step 2 – Create the stitches

Now we’ll create the basic stitch element. I used ShadowBox, but ZSpheres can work just as well, depending on what type of stitching you’re creating. Try to finalise the sculpted stitch and PolyPaint as much as possible at this stage, since they’ll be duplicated quite a few times, depending on your model. Keep the polycount at the lowest Subdivision level as possible so that it’s easy to alter for different surface features along the gash.

Step 3 – Stitch placement

Duplicate the new stitch SubTool and use the Transpose Move, Rotate and Scale tools to align it with the first set of stitch holes along the gash. Always keep your original stitch SubTool in case you need a fresh duplicate; the repeated duplicating and distorting for each new stitch can add up over time. When you place a stitch, let it intersect a little with the skin surface – this overlap will become skin folds later.

Step 4 – Tension lines and skin folds

Next, sculpt the skin around the stitches to add tension where the skin is pulled tight, and folds where the stitching is causing it to bunch up. With the skin SubTool active, click the Transp button in the lower right corner of the viewport to activate transparency. In this mode, your brush will ignore the ghosted SubTools, enabling us to sculpt under and around the stitches easily.

Step 5 – Refine the cut

Now we’ll really push the nastiness of the cut we’re stitching closed! Pull the edges of the gash together where the stitches cross it, and leave a little opening in between them. Depending on what type of wound you’re creating, add some jagged rough shapes along the edges. Use the Move Topological brush to affect one side of the cut without affecting the other to easily tweak the shape of the wound.

Step 6 – Gory PolyPainting

Start by drawing a bloody red colour along the cut – assuming your character has red blood, that is! Use the Smooth brush in RGB mode to blend the surrounding skin colour with the red of the inflamed wound. Along the ridges and bumps, add a light skin tone and keep the darker reds to the crevices and cuts. You can also use the DragRect stroke with an interesting alpha and low RGB intensity to add a sickly quality to the wound!

Expert tip: Auto Masking brushes

ZBrush 4 includes a Move brush that uses the new Topological Auto Masking mode, but you can use this and other Auto Masking modes for many of the brushes. These features can be found in the Brush menu, under the Auto Masking rollout. My two favourites are the Backface and Topological masks.

The Backface mask is great for working on thin objects, preventing the brush from affecting the other side of a mesh if it’s within the brush’s radius. The Topological mask affects only the section of geometry you began on, ignoring other pieces of nearby non-contiguous geometry – ie moving only the top lip of a closed mouth.